(CNN) -- A man whose left arm was bitten off by a 600-pound alligator is fortunate to be alive, thanks in part to five nurses picnicking nearby.

The alligator was killed and the man's arm was removed from its belly, officials said.

Bill Hedden, 59, was snorkeling in a South Carolina lake on Sunday when the 12-foot-long gator attacked, according to witnesses.

"Suddenly we had commotion and we saw a guy right here. He's bleeding profusely. We thought he was just kidding," witness Jerome Bien told CNN affiliate WCSC-TV in Charleston.

Capt. Bill Salisbury of the Berkeley County Rescue Squad said the victim "was able to run up the bank to a picnic area, where a lot of people were. They saw what was happening and called 911." Watch nurses describe how they helped victim »

Among the group nearby at Lake Moultrie were five registered nurses, who were able to put ice on his wound and keep him awake until paramedics could arrive, CNN affiliate WSOC-TV.

"One of the ... [nurses kept] on encouraging him to breathe and because he was turning blue," nurse Jo Masauding told WCSC-TV.

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"He was very conscious and asking for his wife, to call his wife, to make sure she knew what happened to him," Masauding said.

Hedden was taken to the Medical University of South Carolina, where he was reported to be in critical condition.

Department of Natural Resources officers killed the alligator, and Salisbury said Hedden's arm was retrieved from the gator's belly, put on ice and taken to the hospital. Doctors were evaluating whether it could be reattached.

Wildlife officials said it was one of the worst gator attacks in the state, WSOC reported.E-mail to a friend